Prep the ingredients per the instructions above.
Preheat the oven broiler to medium. Place tomatoes, jalapeño, chunked onion, and garlic on a foil-lined baking sheet and broil, undisturbed, until charred on all sides, about 2 to 3 minutes for garlic, 4 to 5 minutes for jalapeno and onion, 10 to 12 for tomatoes. Transfer to a blender and puree on low until the salsa is almost smooth but some chunks remain. (Don’t be tempted to put it on high or you will incorporate air into the salsa and it will look and taste more like a smoothie than a salsa.) Transfer to a medium bowl, stir in lime juice, and season with salt to taste. Set aside.
Heat half of the oil in a skillet over medium-high heat. Cook chorizo, breaking up large clumps with a spoon, until browned and fully cooked, about 6 to 8 minutes. Transfer to a small bowl, leaving oil behind. Add the diced onion, stirring occasionally, until lightly browned. Add the beans and their liquid. Bring to a boil and cook, stirring occasionally, until liquid is reduced to a thick consistency, about 5 to 10 minutes.
Heat the remaining oil in a nonstick skillet over medium heat. Crack eggs into skillet, leaving space around each one, and cook until whites are set and edges are crisp, about 4 minutes. Season with kosher salt.
Spread the beans over each tostada;, top with chorizo, egg, salsa, a sprinkle of queso fresco, and avocado slices. Enjoy with orange juice.